Method of depositing material on stepped structure

ABSTRACT

A method for depositing material is disclosed. An exemplary method includes positioning a substrate provided with a stepped structure comprising a top surface, a bottom surface, and a sidewall in a reaction chamber; controlling a pressure of the reaction chamber to a process pressure; providing a precursor; providing a reactant; and, providing a plasma with a RF plasma power, wherein by simultaneously providing the precursor, the reactant, and the plasma while controlling the process pressure to less than or equal to 200 Pa and controlling the RF plasma power to more than or equal to 0.21 W per cm 2  the material is deposited on the top surface, the bottom surface, and the sidewall of the stepped structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Application No. 63/091,871,filed on Oct. 14, 2020 in the United States Patent and Trademark Office,the disclosure of which is incorporated herein in its entirety byreference.

FIELD OF INVENTION

The present disclosure relates generally to a method of depositingmaterial and more particularly, to a method of depositing siliconnitride on a stepped structure of a substrate via plasma enhancedchemical vapor deposition (PECVD).

BACKGROUND OF THE DISCLOSURE

High density storage devices have been proposed using a 3D stackedmemory structure, which includes a stepped structure. It is required toform a thin film on a selected area of the stepped structure.

Plasma Enhanced Atomic Layer Deposition (PEALD) may be applied to formthe thin film on the stepped structure. However, ALD has a slow rate offilm deposition.

Any discussion, including discussion of problems and solutions, setforth in this section, has been included in this disclosure solely forthe purpose of providing a context for the present disclosure, andshould not be taken as an admission that any or all of the discussionwas known at the time the invention was made or otherwise constitutesprior art.

SUMMARY OF THE DISCLOSURE

This summary is provided to introduce a selection of concepts in asimplified form. These concepts are described in further detail in thedetailed description of example embodiments of the disclosure below.This summary is not intended to identify key features or essentialfeatures of the claimed subject matter, nor is it intended to be used tolimit the scope of the claimed subject matter.

In various embodiments, a method of depositing material on a steppedstructure is provided. The method may comprise positioning a substrateprovided with a stepped structure comprising a top surface, a bottomsurface, and a sidewall in a reaction chamber; controlling a pressure ofthe reaction chamber to a process pressure; providing a precursor;providing a reactant; and, providing a plasma with a RF plasma powerwherein by simultaneously providing the precursor, the reactant, and theplasma while controlling the process pressure to less than or equal to200 Pa and controlling the RF plasma power to more than or equal to 0.21W per cm² the material is deposited on the top surface, the bottomsurface, and the sidewall of the stepped structure.

In various embodiments, the RF frequency may be in the range of 13.55 to27.13 Hz.

In various embodiments, the method may comprise depositing siliconnitride (SiN) on the top surface, the bottom surface, and the sidewallof the stepped structure.

In various embodiments, the method may comprise providing a precursorcomprising a halogenated silane. In various embodiments, the halogenatedsilane may be dichlorosilane, trichlorosilane, or hexachlorodisilane.

In various embodiments, the reactant may comprise a nitrogen reactant.In various embodiments, the nitrogen reactant may be NH₃.

In various embodiments, positioning the substrate in the reactionchamber may comprise positioning the substrate in between, and parallelto two electrodes and the plasma may be provided by applying RF plasmapower to at least one of two electrodes.

In various embodiments, the wet etch rate of the material deposited onthe sidewall divided by the wet etch rate of the material deposited onthe top may be larger than 2.5.

In various embodiments, the method may further comprise providing anetchant to etch a sidewall portion of the deposited material to removethe side wall portion.

In various embodiments, providing an etchant may comprise providing asolution of hydrogen fluoride (HF). In various embodiments, providing anetchant may comprise providing a solution of phosphoric acid.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

A more complete understanding of exemplary embodiments of the presentdisclosure can be derived by referring to the detailed description andclaims when considered in connection with the following illustrativefigures.

FIG. 1 is a schematic representation of a PECVD (plasma-enhancedchemical vapor deposition) apparatus for depositing a dielectric filmusable in an embodiment of the present invention;

FIG. 2 is a timing chart of a PECVD process;

FIG. 3 is a schematic diagram of showing a model of ion bombardment andimpurities concentration in a film on a top surface and a bottom surfaceand a sidewall of a stepped structure;

FIG. 4A is a schematic diagram of showing a film on a top surface and abottom surface and a sidewall of a trench structure; and

FIG. 4B is a schematic diagram of showing a film on a top surface and abottom surface and a sidewall of the trench structure after wet etching.

It will be appreciated that elements in the figures are illustrated forsimplicity and clarity and have not necessarily been drawn to scale. Forexample, the dimensions of some of the elements in the figures may beexaggerated relative to other elements to help understanding ofillustrated embodiments of the present disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Although certain embodiments and examples are disclosed below, it willbe understood by those in the art that the disclosure extends beyond thespecifically disclosed embodiments and/or uses of the disclosure andobvious modifications and equivalents thereof. Thus, it is intended thatthe scope of the disclosure should not be limited by the particularembodiments described herein.

The illustrations presented herein are not meant to be actual views ofany particular material, apparatus, structure, or device, but are merelyrepresentations that are used to describe embodiments of the disclosure.

As used herein, the term “substrate” may refer to any underlyingmaterial or materials that may be used, or upon which, a device, acircuit, or a film may be formed.

As used herein, the term “film” and “thin film” may refer to anycontinuous or non-continuous structures and material deposited by themethods disclosed herein. For example, “film” and “thin film” couldinclude 2D materials, nanorods, nanotubes, or nanoparticles or evenpartial or full molecular layers or partial or full atomic layers orclusters of atoms and/or molecules. “Film” and “thin film” may comprisematerial or a layer with pinholes, but still be at least partiallycontinuous.

The process cycle may be performed using any suitable apparatusincluding an apparatus illustrated in FIG. 1 , for example. FIG. 1 is aschematic view of a PECVD apparatus, desirably in conjunction withcontrols programmed to conduct the sequences described below, usable insome embodiments of the present invention. In this figure, by providinga pair of electrically conductive flat-plate electrodes 4, 2 in paralleland facing each other in the interior 11 (reaction zone) of a reactionchamber 3, applying HRF power (13.56 MHz or 27 MHz) 20 to one side, andelectrically grounding the other side 12, a plasma may be excitedbetween the electrodes. A temperature regulator may be provided in alower stage 2 (the lower electrode), and a temperature of a substrate 1placed thereon may be kept constant at a given temperature. The upperelectrode 4 may serve as a shower plate as well, and precursor andreactant gas may be introduced into the reaction chamber 3 through a gasline 21 and a gas line 22, respectively, and through the shower plate 4.Additionally, in the reaction chamber 3, a circular duct 13 with anexhaust line 7 may be provided, through which gas in the interior 11 ofthe reaction chamber 3 may be exhausted.

Further, a transfer chamber 5 disposed below the reaction chamber 3 maybe provided with a seal gas line 24 to introduce seal gas into theinterior 11 of the reaction chamber 3 via the interior 16 (transferzone) of the transfer chamber 5 wherein a separation plate 14 forseparating the reaction zone and the transfer zone may be provided (agate valve through which a wafer is transferred into or from thetransfer chamber 5 is omitted from this figure). The transfer chambermay be also provided with an exhaust line 6. In some embodiments, thedeposition of multi-element film and surface treatment may be performedin the same reaction space, so that all the steps may continuously beconducted without exposing the substrate to air or otheroxygen-containing atmosphere. In some embodiments, a remote plasma unitmay be used for exciting a gas.

In some embodiments, a multiple chamber module (two or four chambers orcompartments for processing wafers disposed close to each other) may beused, wherein a reactant gas and a noble gas may be supplied through ashared line whereas a precursor gas may be supplied through unsharedlines.

A skilled artisan will appreciate that the apparatus includes one ormore controller(s) (not shown) programmed or otherwise configured tocause the deposition and reactor cleaning processes described elsewhereherein to be conducted. The controller(s) may be communicated with thevarious power sources, heating systems, pumps, robotics, and gas flowcontrollers or valves of the reactor, as will be appreciated by theskilled artisan.

With additional reference to FIG. 2 and FIG. 3 , a method for depositionmaterial is illustrated. The method includes positioning a substrateprovided with a stepped structure comprising a top surface, a bottomsurface, and a sidewall in the reaction chamber 3; controlling apressure of the reaction chamber 3 to a process pressure; providing aprecursor; providing a reactant; and providing a plasma with a RF plasmapower. The material may be deposited on the top surface, the bottomsurface, and the sidewall of the stepped structure by simultaneouslyproviding the precursor, the reactant, and the plasma, which is PlasmaEnhanced Chemical Vapor Deposition (PECVD) process. PECVD is a chemicalvapor deposition process used to deposit thin films from a gas state(vapor) to a solid state on the substrate. Chemical reactions areinvolved in the process, which occur after creation of a plasma of thereacting gases. The precursor gas and reactant gas continue to flow tothe reaction chamber 3 while RF plasma power is continuously applied tothe electrode 4.

By adjusting bombardment of a plasma excited by applying voltage betweentwo electrodes 2, 4 between which the substrate is placed in parallel tothe two electrodes 2, 4, a top/bottom portion of the dielectric filmformed on the top surface and the bottom surface and a sidewall portionof the dielectric film formed on the sidewalls can be given differentchemical resistance properties. A plasma is a partially ionized gas withhigh free electron content (about 50%), and when a plasma is excited byapplying AC voltage between parallel electrodes 2,4, ions areaccelerated by a self dc bias (VDC) developed between plasma sheath andthe lower electrode 2 and bombard a film on a substrate placed on thelower electrode 2 in a direction perpendicular to the film (the ionincident direction). The ion bombardment may be modulated by tuning thepressure and RF power. The lower the pressure and the higher the power,the higher the ion bombardment becomes, resulting in low impurities intop/bottom portions of film. A pressure of the reaction chamber 3 may becontrolled less than or 200 Pa or less or equal to 150 Pa. RF plasmapower may be controlled more than or equal to 0.21 watt per cm² (150 Wfor 300 mm wafer), preferably 0.28 watt per cm² and more preferably 0.35watt per cm².

In some embodiments, the film may be a SiN film. The SiN film maycomprise providing a precursor comprising halogenated silane and areactant comprising nitrogen-containing reactant. The halogenated silanemay be dichlorosilane (DCS), trichlorosilane, or hexachlorodisilane. Thenitrogen-containing reactant may be NH₃.

In some embodiments, according to the difference in the film propertiesbetween the top/bottom portion of the film and the sidewall portion ofthe film, the sidewall portion of the film is more predominantly etchedthan the other by wet etching. The wet etch rate of the materialdeposited on the sidewall divided by the wet etch rate of the materialdeposited on the top may be larger than 2.5, preferably larger than 3and most preferably larger than 3.5. The wet etching may be conductedusing a solution of hydrogen fluoride (HF), for example.

The present invention is further explained with reference to workingexamples below. However, the examples are not intended to limit thepresent invention. In the examples where conditions and/or structuresare not specified, the skilled artisan in the art can readily providesuch conditions and/or structures, in view of the present disclosure, asa matter of routine experimentation. Also, the numbers applied in thespecific examples can be modified by a range of at least ±50% in someembodiments, and the numbers are approximate.

EXAMPLES Example 1

SiN films were formed on Si substrates (ϕ300 mm) having a steppedstructure by PEALD and PECVD, which were conducted under the conditionsshown in Table 1.

TABLE 1 (numbers are approximate) PEALD PECVD Process 1^(st) 2^(nd)1^(st) 2^(nd) Gas Ar [slm] 1.5 3 0.75 1.5 Flow N2 [slm] 0.5 1 1.5 0.75Rate DCS [slm] 1 1 0.1 0.1 NH3 [slm] 3 0.5 0.5 0.5 BTL1 Ar [slm] 1 20.75 0.75 BTL2 Ar [slm] 1 2 0.75 0.75 Seal N2 [slm] 2 2 0.5 0.5 Pressure[Pa] 533 400 200 150 RF power [W] 100 150 150 250

After taking out the substrate from the reaction chamber, the substratewas subjected to wet etching under the conditions shown in Table 2below.

TABLE 2 (numbers are approximate) Conditions for Wet etching Etchingsolution HF 0.05-5% Etching solution 10 to 50° C. (preferably 15 to 30°C.) temperature Duration of etching 1 sec to 5 min (preferably 1 to 3min) Etching rate 0.1 to 5 nm/min (preferably 0.5 to 2 nm/min)

For wet etching, any suitable single-wafer type or batch type apparatusincluding any conventional apparatuses can be used. Also, any suitablesolution for wet etching including any conventional solutions can beused.

The results are shown in Table 3 and FIG. 4 . WER selectivity is definedby the ratio of WER on the sidewall portion and the WER on the topportion.

TABLE 3 (numbers are approximate) PEALD PECVD Process 1^(st) 2^(nd)1^(st) 2^(nd) Pressure [Pa] 533 400 200 150 RF power [W] 100 150 150 250WER selectivity (Side/Top) 1.9 2.2 1.9 3.8 Depo rate [nm/sec.] 0.03 0.020.63 0.57

As shown in Table 3, the wet etch rate of the sidewall portion increasedas RF power increased and pressure decreased, whereas the wet etch rateof the top portion decreased as the RF power increased and pressuredecreased. The threshold RF power of PECVD process was approximately 150W and the threshold Pressure is 200 Pa. It can be understood that whenRF power applied between the electrodes is higher than approximately 150W and pressure is lower than approximately 200 Pa, the sidewall portionof the film can be removed selectively relative to the top/bottomportions of the film. Further, the deposition rate of PECVD is muchhigher than that of PEALD.

The example embodiments of the disclosure described above do not limitthe scope of the invention, since these embodiments are merely examplesof the embodiments of the invention. Any equivalent embodiments areintended to be within the scope of this invention. Indeed, variousmodifications of the disclosure, in addition to those shown anddescribed herein, such as alternative useful combinations of theelements described, may become apparent to those skilled in the art fromthe description. Such modifications and embodiments are also intended tofall within the scope of the appended claims.

What is claimed is:
 1. A method for depositing material, comprising:positioning a substrate provided with a stepped structure, comprising atop surface, a bottom surface, and a sidewall, in a reaction chamber;controlling a pressure of the reaction chamber to a process pressure;providing a precursor comprising a halogenated silane; providing areactant; and, providing a plasma with a RF plasma power, wherein bysimultaneously providing the precursor, the reactant, and the plasmawhile controlling the process pressure to less than or equal to 200 Paand controlling the RF plasma power density to more than or equal to0.21 W per cm² of a surface of the substrate, the material is depositedon the top surface, the bottom surface, and the sidewall of the steppedstructure.
 2. The method according to claim 1, wherein an RF frequencyof the RF plasma power is in the range of 13.55 to 27.13 MHz.
 3. Themethod according to claim 1, wherein the method comprises depositingsilicon nitride (SiN) on the top surface, the bottom surface, and thesidewall of the stepped structure.
 4. The method according to claim 1,wherein the halogenated silane is dichlorosilane, trichlorosilane orhexachlorodisilane.
 5. The method according to claim 4, wherein thehalogenated silane is trichlorosilane or hexachlorodisilane.
 6. Themethod according to claim 1, wherein the reactant comprises a nitrogenreactant.
 7. The method according to claim 6, wherein the nitrogenreactant is NH₃.
 8. The method according to claim 1, wherein positioningthe substrate in the reaction chamber comprises positioning thesubstrate in between, and parallel to two electrodes and the plasma isprovided by applying RF plasma power to at least one of two electrodes.9. The method according to claim 1, wherein the wet etch rate of thematerial deposited on the sidewall divided by the wet etch rate of thematerial deposited on the top is larger than 2.5.
 10. The methodaccording to claim 1, further comprising providing an etchant to etch asidewall portion of the deposited material to remove the side wallportion.
 11. The method according to claim 10, wherein providing theetchant comprises providing a solution of hydrogen fluoride (HF). 12.The method according to claim 10, wherein providing the etchantcomprises providing a solution of phosphoric acid.
 13. The methodaccording to claim 1, wherein the steps of providing the precursor,providing the reactant, and providing the plasma with a RF plasma powerare continuous during the deposition process.
 14. The method accordingto claim 1, wherein the reactant comprises NH₃ and is provided to thereaction chamber with nitrogen and argon.
 15. The method according toclaim 1, wherein the wet etch rate of the material deposited on thesidewall divided by the wet etch rate of the material deposited on thetop is larger than 3.5.